1. Field of the Invention
The present invention relates to a brake device which applies a braking force to a braking target such as a wheel. Priority is claimed on Japanese Patent Application No. 2011-229524, filed Oct. 19, 2011, the contents of which is incorporated herein by reference.
2. Description of Related Art
As a brake device that applies a braking force to a wheel, there is know for example a device disclosed in Japanese Unexamined Patent Application, First Publication No. 2011-122703.
As shown in FIG. 9 and FIG. 10, a brake device 101 described in the above patent document includes; a brake shoe 102 serving as a damper, a push rod 128, a casing 106, a piston 118, and wedge members 119. The brake shoe 102 applies a braking force to a tread surface S of a wheel. The push rod 128 causes the brake shoe 102 to advance and retreat in a braking direction towards the wheel. The casing 106 supports the push rod 128 in a manner capable of advancing and retreating in the braking direction. The piston 118 is provided inside the casing 106, and advances and retreats on receiving a driving force in the form of air pressure. The wedge members 119 are integrally fixed to the piston 118.
On both sides of the push rod 128 there are provided moving rollers 126. Furthermore, on the casing 106 side there is affixed a pair of fixed rollers 124 which receive a reaction force to the pushing force applied by the piston 118 to the push rod 128.
The two moving rollers 126 are configured so as to advance and retreat in the braking direction, accompanying the back and forth movement of the wedge members 119 in the drive direction orthogonal to the braking direction. That is to say, due to the back and forth movement of the wedge members 119 in the driving direction, the two moving rollers 126 which contact the incline surfaces 122 of the wedge members 119 are pushed in the braking direction. As a result, the push rod 128 advances and retreats in the braking direction.
When the push rod 128 advances or retreats in the braking direction, the push rod 128 causes guide rollers 150, provided coaxially with the moving rollers 126 and outside the moving rollers 126 in the axial direction, to travel along guide rails 151 provided in the casing 106. This restricts the movement direction of the push rod 128 to the braking direction.
However, in the brake device 101 described above, the guide rollers 150 project further to outside of the moving rollers 126 provided on the push rod 128. Consequently, a problem occurs in that the casing 106 is correspondingly larger.